May 30, 2003 COLUMBUS, Ohio – For lactose intolerant adults, drinking fermented milk either eliminated or drastically reduced symptoms related to lactose intolerance. Researchers think that microbes in this fermented milk – called kefir – possess the enzyme that is necessary to digest lactose. Kefir is a little known, and slightly more expensive, alternative to milk. It contains a multitude of bacteria that are thought to break down lactose in the digestive tract.
"Many health claims exist for kefir, including the enhancement of the immune system and improved digestive health, particularly with regard to lactose digestion," said Steven Hertzler, a study co-author and an assistant professor of medical dietetics at Ohio State University.
"We wanted to find out if kefir would improve lactose digestion. The research showed that it did."
The study appears in a recent issue of the Journal of the American Dietetic Association. Hertzler conducted the study with Shannon Clancy, a clinical dietitian at Toledo Hospital in Toledo, Ohio.
Kefir tastes slightly on the tart side and has the consistency of liquid yogurt. To manufacture kefir, producers add clusters of starchy carbohydrate – kefir grains – that contain healthy bacteria and are left to ferment in milk. The grains are filtered out while the live cultures remain.
The researchers asked 15 adults to consume five separate test foods: 2 percent milk; plain kefir; raspberry-flavored kefir; plain yogurt; and raspberry-flavored yogurt. Each food was eaten after a 12-hour fast and followed up by a series of breath hydrogen tests every hour for eight hours. Participants were asked to record any symptoms of lactose intolerance for eight hours after eating each food.
Past studies by other scientists have shown that eating fermented dairy products, such as yogurt, improves lactose digestion. Participants in the current study reported having little or no symptoms associated with lactose intolerance after eating both types of yogurt and kefir. Flatulence was the most-reported symptom. Drinking kefir reduced flatulence frequency by more than half, compared to milk.
Breath hydrogen levels were also significantly lower after consuming the plain and flavored kefir than after drinking milk. Flatulence is the biggest complaint among lactose-intolerant people, Hertzler said, and breath hydrogen is indicative of excessive gas in the digestive tract.
While it's known that lactose intolerant people can tolerate yogurt – it contains healthy bacteria that break down lactose – there has been relatively little scientific information about the potential benefits of kefir.
Kefir might be a better option than yogurt for some lactose intolerant people, Hertzler said, adding that, like yogurt, kefir is a good source of calcium, potassium and protein. But kefir also contains a wider array of microorganisms than yogurt does.
"Both kefir and yogurt improve lactose digestion simply because some of the bacterial cells give up their lives in the intestinal tract, release their enzymes and digest the lactose," Hertzler said. "It's a one-shot deal. However, kefir has additional microorganisms that may be able to colonize the intestines and benefit health further by protecting the intestine against disease-causing bacteria."
Hertzler said he hopes to conduct further studies that explore kefir's potential for improving health.
This study was funded by a grant from Lifeway Foods, Inc., a company that manufactures kefir. Hertzler has no financial connections to Lifeway Foods, Inc.
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